
function Node(value) {
	this.value;
	this.next = null;
	this.pre = null;
}

var node1 = new Node(1)
var node2 = new Node(2)
var node3 = new Node(3)
var node4 = new Node(4)
var node5 = new Node(5)

node1.next = node2;
node2.pre = node1;
node2.next = node3;
node3.pre = node2;
node3.next = node4;
node4.pre = node3;
node4.next = node5;
node5.pre = node4

//双向链表的优点： 无论给出哪个一个节点，都能遍历链表
//        缺点： 多耗费一个引用空间，而且构建 也比较复杂